The invention relates to a spinning system for the production of monofilament yarn, in which a spinning tool comprises a channel section for a polymer melt, said channel section expanding widthwise in a channel portion of the spinning tool into a flow channel in the form of a flattened U (or T-die) and connected to a group of nozzles.
Such a spinning tool is known from DE-B No. 33 34 870.
Such spinning systems are used to spin from polymer melts high-grade yarn, which, owing to its application, e.g. for filter fabrics, breast harnesses, fishing lines etc., must have constant material characteristics within a close tolerance range. The production of a high- pressure-compatible, close-meshed filter fabric requires yarn, firstly, of a constant diameter and, secondly, of a high tearing strength.
With the known spinning system of the kind described in the aforementioned patent specification, the uniform delivery volume of a polymer melt along a two-dimensional channel is provided for by a flow-regulating bar, the variable distance of which from a wall of the two-dimensional channel regulates the volume of polymer melt passing through. Accordingly, the flow-regulating bar must be flexible or must consist of several individual elements, so that it is able lengthwise to form a variable gap with the wall. The polymer melt is accumulated in the two-dimensional channel by the flow-regulating bar, and, according to its set distance from the wall, a defined amount of polymer melt is able to pass through a set gap per unit time.
The flow-regulating bar must be sealed with particular care because of the high product and housing temperatures occurring in the production of monofilament yarn. This is particularly difficult to achieve at temperatures around approx. 300.degree. C. There is also the fact that, as is known, sealing elements of moving machine parts are also more susceptible to malfunction at raised temperatures. If materials undergo different degrees of expansion, the gap between flow-regulating bar and wall must be re-adjusted during operation. This calls for an elaborate monitoring unit for the gap width between wall and flow-regulating bar.
The object of the invention, therefore, is to further develop the spinning system of the aforementioned kind to the extent that, with laminar flow and without separation of flow, the polymer melt is distributed constantly and uniformly over the entire free space of the flattened-U-shaped channel or T-die so that, with maximum reliability of production, the group of nozzles is supplied over its entire width with a constant mass flow of polymer.